1. Field of the Invention
The present invention relates to draft sills for use with railway car trucks and to center pins extending between draft sills and railway car trucks.
2. Description of the Prior Art
In a typical railway freight train, such as that shown at 10 in FIG. 1, railway cars 12, 14 are connected end to end by couplers 16, 18. The couplers 16, 18 are each received in draft sills 20, 22. The draft sills 20, 22 are at the ends of the railway car's center sill, and include center plates that rest in center plate bowls 24 of railway car trucks 26, 28.
As shown in FIG. 2, each typical car truck 26 comprises a pair of side frames 30, 32 supported on wheel sets 34, 36. A hollow bolster 38 extends between and is supported on springs 40 on the side frames. The bolster center plate bowl 24 has a central opening 42. One draft sill with a center plate is supported on each car truck, with the draft sill center plate received within the bolster center plate bowl.
The draft sills typically have a top wall that is usually welded to a shear plate that is connected to the bottom of the railway car. The two draft sills are connected to the two ends of the car center sill that runs the length of the car.
In the event the railway car encounters a bump or other event causing relative vertical motion between the car truck and the draft sill, the shallow center plate bowl may not retain the center plate, and the center plate and center plate bowl could separate and move horizontally with respect to each other so that the draft sill is no longer supported on the bolster center plate bowl. To prevent such relative horizontal motion, center pins have typically been used in the prior art to loosely connect each draft sill to each truck.
In some applications, it has been desirable to lock the center plate and center plate bowl together to limit relative vertical and horizontal movement between these parts. In one prior art assembly, a fabricated draft sill was assembled, with one end of the center pin fixed in the interior of the draft sill with a retainer plate and pins. The other end of the center pin was fixed in the interior of the bolster with a large retainer plate extending through the bolster walls and the center pin. This prior art design had disadvantages: the center pin could not be removed from the fabricated draft sill without disassembling part of the draft sill. In addition, this locking design could not be readily applied to cast draft sills.